1. Technical Field
The present disclosure relates to graphene/oxide semiconductor heterojunction devices and a fabrication method thereof. More particularly, it relates to a Schottky junction device, a p-n heterojunction device, and fabrication methods thereof.
2. Related Art
Graphene is a two-dimensional hexagonal crystal structure of sp2-bonded carbon atoms and has been reported to have interesting physical and electrical properties, including electrons that behave like massless Dirac fermions, and anomalous hall effects. Thus, in recent years, studies on the preparation of high-quality graphene and on the application of graphene to devices have been actively conducted.
Graphene have been prepared by a mechanical exfoliation method, a chemical method employing a reducing agent, and an epitaxial method employing a silicon carbide insulator.
In the mechanical exfoliation method, graphene is prepared from highly ordered pyrolytic graphite (HOPG) using a very delicate mechanical exfoliation technique. In the chemical method, highly ordered pyrolytic graphite (HOPG) is chemically exfoliated using a strong acid in a liquid state, a graphene oxide film resulting from the exfoliated graphite is deposited on a substrate, and then the deposited graphene oxide film is subjected to chemical reduction to produce a large-area graphne. In the epitaxial method, epitaxial graphene is prepared on a SiC (0001) substrate by vacuum heat treatment. However, these methods have disadvantages, for example, in that the electrical properties of graphene are not good, the substrate that can be used is limited, and/or a non-uniform graphene layer is formed.
In recent years, a chemical vapor deposition (CVD) method has been used to prepare graphene. In the CVD method, grapheme is chemically vapor-deposited on a metal substrate such as Ni or Cu using methane gas. This method requires a process of exfoliating graphene grown on such a metal substrate and transferring the exfoliated graphene onto a desired oxide and semiconductor substrate, which cause the whole process to become very complicated and the interface between graphene and the substrate to have defects that can significantly deteriorate the behavior characteristics of a device manufactured using the graphene/substrate.
Thus, a technique of growing graphene directly on an oxide or a semiconductor is still required.